The thermal performance of the heat exchanger is strongly influenced by the supporting structure.Corrugated baffle enhances flow field disturbance and heat transfer through its complex and changeable flow channel.In o...The thermal performance of the heat exchanger is strongly influenced by the supporting structure.Corrugated baffle enhances flow field disturbance and heat transfer through its complex and changeable flow channel.In order to enhance the thermal performance of the torsional flow heat exchanger(TFHX),the sinusoidal corrugated baffle(SCB)is used to replace the flat baffle(FB)and the full-section cycle model of the torsional flow heat exchanger with sinusoidal corrugated baffle(TFHX-SCB)is established.Computational fluid dynamics(CFD)method was used to discuss the flow resistance characteristics of the shell-side of heat exchangers.The results show that the SCB can improve the turbulence intensity and the uniformity of the flow field between the adjacent baffles.The combination of structural configurations on the shell-side of TFHX-SCB is analyzed by the central composite design(CCD)-response surface method(RSM).When the amplitude of the SCB is 1.37 mm,the cycles of the SCB are 4.42;the initial phase of the SCB is 112.73°,and the combination of heat transfer coefficient and comprehensive performance is optimal.Compared with the original structure,the heat transfer coefficient is increased by 11.58%,and the comprehensive performance is increased by 5.48%.The laser doppler velocimetry(LDV)experimental device irradiated the specified measurement point,and the dependability and accuracy of numerical simulation methods were verified.The research conclusion provides a basic theory for the structural development of the TFHX.展开更多
This paper investigates surface energy effects, including the surface shear modulus, the surface stress, and the surface density, on the free torsional vibration of nanobeams with a circumferential crack and various b...This paper investigates surface energy effects, including the surface shear modulus, the surface stress, and the surface density, on the free torsional vibration of nanobeams with a circumferential crack and various boundary conditions. To formulate the problem, the surface elasticity theory is used. The cracked nanobeam is modeled by dividing it into two parts connected by a torsional linear spring in which its stiffness is related to the crack severity. Governing equations and corresponding boundary conditions are derived with the aid of Hamilton＇s principle. Then, natural frequencies are obtained analytically, and the influence of the crack severity and position, the surface energy, the boundary conditions, the mode number, and the dimensions of nanobeam on the free torsional vibration of nanobeams is studied in detail. Results of the present study reveal that the surface energy has completely different effects on the free torsionl vibration of cracked nanobeams compared with its effects on the free transverse vibration of cracked nanobeams.展开更多
Torsional vibrations of coated hollow poroelastic spheres are studied employing Biot’s theory of wave propagation in poroelastic solid. The dilatations of solid and liquid media are zero, therefore the frequency equa...Torsional vibrations of coated hollow poroelastic spheres are studied employing Biot’s theory of wave propagation in poroelastic solid. The dilatations of solid and liquid media are zero, therefore the frequency equation of torsional vibrations is same both for a permeable and an impermeable surface. The coated poroelastic sphere consists of an inner hollow poroelastic sphere bounded by and bonded to a sphere made of distinct poroelastic material. The inner sphere is designated as core and outer sphere as casing. Core and casing are bonded at the curved surfaces. The inner and outer boundaries of the coated hollow poroelastic sphere are free from stress and at the interface of core and casing the displacement and stresses are continuous. It is assumed that the each material of coated sphere is homogeneous and isotropic. The frequency equation of torsional vibrations of a coated poroelastic hollow sphere is obtained when the material of the core vanishes. Also a coated poroelastic solid sphere is obtained as the limiting case of the frequency equation of coated hollow poroelastic sphere when the inner radius of core approaches to zero. Non-dimensional frequency as a function of ratio of thickness of core to that of inner radius of core is determined and analyzed. It is observed that the frequency and dispersion increase with the increase of the thickness of the coating.展开更多
基金supported by National Natural Science Foundation of China(Grant No.21776263)。
文摘The thermal performance of the heat exchanger is strongly influenced by the supporting structure.Corrugated baffle enhances flow field disturbance and heat transfer through its complex and changeable flow channel.In order to enhance the thermal performance of the torsional flow heat exchanger(TFHX),the sinusoidal corrugated baffle(SCB)is used to replace the flat baffle(FB)and the full-section cycle model of the torsional flow heat exchanger with sinusoidal corrugated baffle(TFHX-SCB)is established.Computational fluid dynamics(CFD)method was used to discuss the flow resistance characteristics of the shell-side of heat exchangers.The results show that the SCB can improve the turbulence intensity and the uniformity of the flow field between the adjacent baffles.The combination of structural configurations on the shell-side of TFHX-SCB is analyzed by the central composite design(CCD)-response surface method(RSM).When the amplitude of the SCB is 1.37 mm,the cycles of the SCB are 4.42;the initial phase of the SCB is 112.73°,and the combination of heat transfer coefficient and comprehensive performance is optimal.Compared with the original structure,the heat transfer coefficient is increased by 11.58%,and the comprehensive performance is increased by 5.48%.The laser doppler velocimetry(LDV)experimental device irradiated the specified measurement point,and the dependability and accuracy of numerical simulation methods were verified.The research conclusion provides a basic theory for the structural development of the TFHX.
文摘This paper investigates surface energy effects, including the surface shear modulus, the surface stress, and the surface density, on the free torsional vibration of nanobeams with a circumferential crack and various boundary conditions. To formulate the problem, the surface elasticity theory is used. The cracked nanobeam is modeled by dividing it into two parts connected by a torsional linear spring in which its stiffness is related to the crack severity. Governing equations and corresponding boundary conditions are derived with the aid of Hamilton＇s principle. Then, natural frequencies are obtained analytically, and the influence of the crack severity and position, the surface energy, the boundary conditions, the mode number, and the dimensions of nanobeam on the free torsional vibration of nanobeams is studied in detail. Results of the present study reveal that the surface energy has completely different effects on the free torsionl vibration of cracked nanobeams compared with its effects on the free transverse vibration of cracked nanobeams.
文摘Torsional vibrations of coated hollow poroelastic spheres are studied employing Biot’s theory of wave propagation in poroelastic solid. The dilatations of solid and liquid media are zero, therefore the frequency equation of torsional vibrations is same both for a permeable and an impermeable surface. The coated poroelastic sphere consists of an inner hollow poroelastic sphere bounded by and bonded to a sphere made of distinct poroelastic material. The inner sphere is designated as core and outer sphere as casing. Core and casing are bonded at the curved surfaces. The inner and outer boundaries of the coated hollow poroelastic sphere are free from stress and at the interface of core and casing the displacement and stresses are continuous. It is assumed that the each material of coated sphere is homogeneous and isotropic. The frequency equation of torsional vibrations of a coated poroelastic hollow sphere is obtained when the material of the core vanishes. Also a coated poroelastic solid sphere is obtained as the limiting case of the frequency equation of coated hollow poroelastic sphere when the inner radius of core approaches to zero. Non-dimensional frequency as a function of ratio of thickness of core to that of inner radius of core is determined and analyzed. It is observed that the frequency and dispersion increase with the increase of the thickness of the coating.
